Why are small-breed dogs more at risk of “Degenerative Mitral Valve Disease (MMVD)” than other breeds?

Heart disease is one of the most common health problems in dogs, especially in small breeds aged 7 years and older. Among them, Degenerative Mitral Valve Disease (MMVD) is found at the highest incidence. This condition occurs when the heart valve does not close properly, causing blood to leak backward. As a result, the heart has to work harder, which can eventually lead to an enlarged heart and heart failure.

Breeds commonly at higher risk include:

• Pomeranian
• Chihuahua
• Shih Tzu
• Poodle

Why are small-breed dogs more at risk?

1. Genetic factors Many small breeds have a genetic predisposition that makes their heart valves more prone to degeneration. The risk increases progressively with age.
2. Heart structure characteristics Small-breed dogs are more likely to develop problems involving the heart valves, whereas large-breed dogs more commonly experience issues related to the heart muscle itself.
3. Longer lifespan Small breeds generally live longer. This allows degenerative changes in organs to accumulate over time, eventually becoming clinically apparent in their senior years.

Warning signs to watch for:

• Chronic coughing, especially at night
• Easy fatigue or shortness of breath
• Weakness or fainting
• Rapid breathing even at rest

Regular heart check-ups from an early stage are key to prolonging life and slowing disease progression — helping your little one’s heart stay with you as long as possible 💙

Article by: Dr. Pui (Dr. Patthawann), DVM

Veterinarian, Cardiology and Cardiovascular Center

Surgery and Anesthesia Center

Thonglor Pet Hospital, Pattaya Branch